Extcon: fix section mismatch in extcon_gpio.c

Fix the section mismatch be renaming the struct platform_driver
variable.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>